Silicon-based visible and near-infrared optoelectric devices

• US 10,374,109 B2
• Filed: 10/16/2017
• Issued: 08/06/2019
• Est. Priority Date: 05/25/2001
• Status: Expired due to Fees

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Mazur, Eric, Carey, James Edward
• Primary Examiner(s): Reames, Matthew L
• Application Number:
  US15/784,756
• Publication Number:
  US 20180083146A1
• Time in Patent Office: 659 Days
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02686 Pulsed laser beam
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 31/0236 Special surface textures
• CPC Class Codes: H01L 31/02363 of the semiconductor body itself, e.g. textured active layers
• CPC Class Codes: H01L 31/028 including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/0288 characterised by the doping material
• CPC Class Codes: H01L 31/036 characterised by their crystalline structure or particular orientation of the crystalline planes
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1864 Annealing
• CPC Class Codes: H01L 31/1872 Recrystallisation
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10S 438/94 Laser ablative material removal

Abstract

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Claims

1. A method for processing a silicon semiconductor substrate, comprising:

irradiating a surface of the silicon substrate with a plurality of circularly polarized short laser pulses so as to generate a plurality of surface structures,

wherein the short laser pulses have a pulse width in a range of about 50 femtoseconds to about 50 picoseconds, a central wavelength in a range of about 200 nm to about 1200 nm, and a fluence in a range of about 1 kJ/m² to about 12 kJ/m², and

wherein the plurality of surface structures have a substantially circular base.

2. The method of claim 1, further comprising exposing one or more locations of said semiconductor surface to a dopant during said step of irradiating the surface.

3. The method of claim 2, wherein said dopant is an electron-donating dopant.

4. The method of claim 1, wherein said short laser pulses are applied to said substrate surface at a repetition rate in a range of about 1 kHz to about 1 MHz.

5. The method of claim 1, wherein the dopant comprises any of sulfur, nitrogen, chlorine, tellurium, and selenium.

6. The method of claim 1, wherein the fluence is greater than 1 kJ/m².

7. The method of claim 1, wherein the fluence is greater than 3 kJ/m².

8. The method of claim 1, wherein the fluence is in a range of 3 kJ/m² to about 10 kJ/m².

9. The method of claim 1, wherein the fluence is in a range of 3 kJ/m² to about 8 kJ/m².

10. The method of claim 1, wherein the fluence is in a range of 1 kJ/m² to about 4 kJ/m².

11. The method of claim 1, wherein the fluence is about 4 kJ/m².

12. The method of claim 1, wherein the pulse width is in a range of about 50 to about 500 femtoseconds.

13. The method of claim 1, wherein the pulse width is about 100 femtoseconds.

14. The method of claim 1, wherein the central wavelength is about 400 nm.

15. The method of claim 1, wherein the pulses are applied to the substrate surface at a repetition rate in a range to about 50 MHz.

16. The method of claim 2, wherein the step of exposing comprises depositing the dopant over the silicon surface exposed to laser pulses.

17. The method of claim 2, wherein the step of exposing comprises depositing the dopant over the irradiated surface of the silicon substrate.